21001115220 has 24 divisors (see below), whose sum is σ = 58803122784. Its totient is φ = 5600297376.

The previous prime is 21001115209. The next prime is 21001115249. The reversal of 21001115220 is 2251110012.

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a self number, because there is not a number n which added to its sum of digits gives 21001115220.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 175009234 + ... + 175009353.

It is an arithmetic number, because the mean of its divisors is an integer number (2450130116).

Almost surely, 2^21001115220 is an apocalyptic number.

21001115220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21001115220 is an abundant number, since it is smaller than the sum of its proper divisors (37802007564).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21001115220 is a wasteful number, since it uses less digits than its factorization.

21001115220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 350018599 (or 350018597 counting only the distinct ones).

The product of its (nonzero) digits is 40, while the sum is 15.

Adding to 21001115220 its reverse (2251110012), we get a palindrome (23252225232).

The spelling of 21001115220 in words is "twenty-one billion, one million, one hundred fifteen thousand, two hundred twenty".